The following are prior art to the present invention: U.S. Pat. No. 3,726,605 and German patent specifications Nos. 962,762, 1,001,056, 1,933,070, 1,935,872; "Wirkungsgrade von Turbinen und ihre Abhaengigkeit von der Bauart", Elektrizitaetswirtschaft 1953, page 231-236, 266-270.
A fluid-flow machine is known having at least one substantially disc-shaped rotor containing fluid-flow channels whose inlet openings located on the one front side of said rotor are disposed at a different distance from the axis of rotation than the outlet openings terminating at the other front side and connected with said inlet openings through a substantially radial connecting section respectively, said inlet and outlet openings being formed such that a tangential and an axial component of the relative speed of the fluid-flow medium, occur respectively therein, the axial components being directed in the same direction and the tangential components being directed in the opposite direction.
A fluid-flow machine of this type having an axial-radial-axial flow path is described in the applicant's article "Die DS-Maschine, eine Stroemungsmaschine fuer kleine Schnellaufzahlen" published in the periodical "Brennstoff, Waerme, Kraft", 1970, pages 509-512.
In this known construction, the flow path adjacent the inlet and outlet openings is defined externally by a curved guide surface and internally by a rounded edge. The radii of curvature are located in a plane which forms an angle with the flow speed in the outer rotor opening. As the flow is redirected between the axial-tangential direction in the opening and the radial direction in the connecting section of the rotor, a relative motion with respect to the curvature path therefore occurs which results in flow losses. Since the flow path is restricted by a rectangular cross-section all along the path, additional flow losses occur in the radial connecting section due to secondary flows about the defining edges when the angle between the relative speeds in the axial sections deviates considerably from 90 degrees.